Electrolyte-dependent electrosynthesis and activity of cobalt-based water oxidation catalysts

Electrolysis of Co ²⁺ in phosphate, methylphosphonate, and borate electrolytes effects the electrodeposition of an amorphous highly active water oxidation catalyst as a thin film on an inert anode. Electrodeposition of a catalytically competent species immediately follows oxidation of Co ²⁺ to Co ³⁺ in solution. Methylphosphonate and borate electrolytes support catalyst activity comparable to that observed for phosphate. Catalytic activity for O ₂ generation in aqueous solutions containing 0.5 M NaCl is retained for catalysts grown from phosphate electrolyte.